immuno 002 innate immunity part 2 (inflammation interferons complement proteins sepsis) #05
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what are acute phase proteins?
they are proteins that are synthesized by the liver and released into the plasma of the blood in response to inflammation.
true or false? complement can only be activated by the adaptive immune system
false. it doesn't have to be activated by the adaptive immune system
describe briefly what complement proteins are and where they are found
complement proteins are a system of small proteins found in the blood
when there is no immune response, what happens to the complement proteins?
they circulate as inactive precursors
right after complement is activated, what steps are taken to mount the complement system attack?
infection triggers complement activation, which proceeds by a series, or cascade, of enzymatic reactions involving proteases, in which each protease cleaves and activates the next enzyme in the pathway
what is the most important component of the complement system?
complement component 3 (C3)
why is the complement system named as it is?
it was discovered as components of plasma that augment the opsonization of bacteria by antibodies and allows antibodies to kill some bacteria. This activity was said to complement the antibacterial activity of the antibody, hence the name
what does the C3b fragment of C3 do?
some of the C3b fragments become covalently bound to the pathogen's surface. This attachment of the C3b to pathogen surfaces is the essential function of the complement system; it is called complement fixation because C3b becomes firmly fixed to pathogen
what does the C3a fragment do?
the soluble C3a fragment also contribtes to the body's defenses by acting as a chemoattractant to recruit effector cells, including phagocytes, from the blood to the site of infection
what happens to complement component 3 (C3) when the complement system is activated?
it gets cleaved by a protease to C3a and C3b
what are the three functions that complement has?
1. recruitment of inflammatory cells
2. Opsonization of pathogens, facilitating uptake and killing by phagocytes
3. perforation of pathogen cell membranes
true or false? C-reactive protein is a part of the complement system
false, it is a part of the acute phase reactants
what are the three pathways by which complement is activated?
1. alternative pathway
2. lectin pathway
3. classical pathway
describe the alternative pathway
this pathway works at the start of infection. it doesn't require activation by adaptive immune system. It uses pathogen surface to create local environment conducive to complement activation
what are anaphylatoxins?
small complement fragments (C3a, C5a, etc) released during complement activation induce local inflammation
what percentage f serum proteins are protease inhibitors?
why are protease inhibitors important?
colonization of human tissues by pathogens is dependent on pathogen's proteases that degrade human tissues
what are the two classes of protease inhibitors?
serpins and α-macroglobulins
what are cytokines?
small secreted proteins, which regulate behavior of other cells; they mediate and regulate immunity, inflammation, cell growth and differentiation, and hematopoiesis
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